Many systems for controlling the steering of machines have included mechanical systems in which cables and other mechanisms are arranged so that the rear wheels can be steered in conjunction with the front wheels. Today, most systems use hydraulic pumps and various hydraulic valves and other components to control the steering of the vehicle. Likewise, electronically controlled four wheel steering systems have been used in which electronic controls select the steering mode and provide for independently controlling the various steered wheels on the machine. In the systems used today, the control valves are spool type valves which, as is well known, have varying degrees of leakage between the spool and the bore in which the spool is slidably disposed. In an all wheel steer vehicle, in which the rear wheels are to be steered in conjunction with the front wheels, the leakage across a spool-type valve can result in the front and rear wheels becoming out of sync. There have been various attempts at trying to keep the front and rear steered wheels in synchronization by using various electronic controls and/or other mechanical linkage-type controls. These known types of mechanisms to control synchronization between the front and rear steered wheels results in added complexity and cost.
The present invention is directed to overcoming one or more of the problems as set forth above.